[HTML][HTML] Demarcated thresholds of tumor-specific CD8 T cells elicited by MCMV-based vaccine vectors provide robust correlates of protection
E Beyranvand Nejad, RB Ratts, E Panagioti… - … for immunotherapy of …, 2019 - Springer
Journal for immunotherapy of cancer, 2019•Springer
Background The capacity of cytomegalovirus (CMV) to elicit long-lasting strong T cell
responses, and the ability to engineer the genome of this DNA virus positions CMV-based
vaccine vectors highly suitable as a cancer vaccine platform. Defined immune thresholds for
tumor protection and the factors affecting such thresholds have not well been investigated in
cancer immunotherapy. We here determined using CMV as a vaccine platform whether
critical thresholds of vaccine-specific T cell responses can be established that relate to tumor …
responses, and the ability to engineer the genome of this DNA virus positions CMV-based
vaccine vectors highly suitable as a cancer vaccine platform. Defined immune thresholds for
tumor protection and the factors affecting such thresholds have not well been investigated in
cancer immunotherapy. We here determined using CMV as a vaccine platform whether
critical thresholds of vaccine-specific T cell responses can be established that relate to tumor …
Background
The capacity of cytomegalovirus (CMV) to elicit long-lasting strong T cell responses, and the ability to engineer the genome of this DNA virus positions CMV-based vaccine vectors highly suitable as a cancer vaccine platform. Defined immune thresholds for tumor protection and the factors affecting such thresholds have not well been investigated in cancer immunotherapy. We here determined using CMV as a vaccine platform whether critical thresholds of vaccine-specific T cell responses can be established that relate to tumor protection, and which factors control such thresholds.
Methods
We generated CMV-based vaccine vectors expressing the E7 epitope and tested these in preclinical models of HPV16-induced cancer. Vaccination was applied via different doses and routes (intraperitoneal (IP), subcutaneous (SC) and intranasal (IN)). The magnitude, kinetics and phenotype of the circulating tumor-specific CD8+ T cell response were determined. Mice were subsequently challenged with tumor cells, and the tumor protection was monitored.
Results
Immunization with CMV-based vaccines via the IP or SC route eliciting vaccine-induced CD8+ T cell responses of > 0.3% of the total circulating CD8 T cell population fully protects mice against lethal tumor challenge. However, low dose inoculations via the IP or SC route or IN vaccination elicited vaccine-induced CD8+ T cell responses that did not reach protective thresholds for tumor protection. In addition, whereas weak pre-existing immunity did not alter the protective thresholds of the vaccine-specific T cell response following subsequent immunization with CMV-based vaccine vectors, strong pre-existing immunity inhibited the development of vaccine-induced T cells and their control on tumor progression.
Conclusions
This study highlight the effectiveness of CMV-based vaccine vectors, and shows that demarcated thresholds of vaccine-specific T cells could be defined that correlate to tumor protection. Together, these results may hold importance for cancer vaccine development to achieve high efficacy in vaccine recipients.
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